On Wednesday morning, Sen. Robert Byrd (D-W.Va.) officially became the longest-serving member in the history of the United States Congress.

Elected to the House of Representatives in 1952, then to the Senate in 1958, Byrd has now surprassed the record set by the late Sen. Carl Hayden (D-Ariz.). Hayden represented Arizona in the House from 1912 to 1927 and then in the Senate until 1969.

The West Virginia Democrat has set a number of records during his time in the upper chamber. Byrd has cast 18,500 votes and has held more leadership positions than any other senator in history. He has presided over both the shortest session of the Senate ("less than a second," according to Majority Leader Harry Reid's, D-Nev., office) and for the longest continuous period of any senator (21 hours). He is the only senator to have been elected to nine terms.

Byrd, who has been in Congress longer than President Barack Obama has been alive, started serving the same day Alaska became a state.

“I am so deeply grateful to the people of the great state of West Virginia for demonstrating such confidence in me and enabling me to reach this momentous milestone," Byrd said in a statement. "My only regret is that my beloved wife, companion and confidante, my dear Erma, is not here with me to witness this wonderful day."

Though Byrd boasts a 97.9 percent attendance record in the Senate, he's missed votes recently due to health issues. Democrats hope he'll be in good enough health to vote for cloture on a healthcare bill sometime in the next few weeks.

“There will never be another senator like Sen. Byrd, and today’s milestone is another record that will never be broken," Reid said.